The goal of this project is to determine the structure of the C-terminal domain of the HIV-1 capsid protein. This domain mediates dimerization of HIV-1 capsid and functions in the assembly of HIV-1 virions. Using a rotating anode source, we have collected data from crystals of native and selenomethionylated protein. Multiwavelength data collection at SSRL is expected to allow elucidation of this important structure. This result will open a new target for the structure-based design of anti AIDS therapeutics.